(a) Field of the Invention
This invention relates to a bearing system for a rotating machine and, more specifically, to a magnetic bearing system.
(b) Description of the Related Art
Oil-retaining bearings and ball bearings, for today's rotating machines, are commonly used to provide a shaft with radial support and free rotation. However, the decrease of the oil quantity contained in an oil-retaining bearing due to long-term usage of the machine or poor sealing of the system can increase the friction force between the oil-retaining bearing and the shaft and results in accompanied high-temperature and noise. Therefore, oil-retaining bearings are becoming less capable of satisfying the requirements of high-performance rotation machines. On the other hand, ball bearings have a problem of wear variation for each rolling ball and thus cause unexpected vibration of the motor during operation and, in turn, produce big noise.
FIG. 1 is a partially sectional view of a conventional fan motor 1, wherein a shaft 111 on a rotor 11 is contained inside a shaft hole 121 on a stator seat 12. As illustrated in FIG. 1, the fan motor 1 has two ball bearings 13 and 14 to constrain the shaft 111, preventing possible radial run out of the shaft 111 as well as providing radial support for the shaft 111. A spring 15 is also used to axially support the shaft 111 and a C retaining ring 16 is used to fix the shaft 111. However, the above-mentioned wear problem of the ball bearings 13 and 14 and the large radial contacting surface of the fan motor shaft 111 with the ball bearings 13 and 14, the spring 15 and the C retaining ring 16 can result in very loud noise and high temperature when the fan motor 1 is in operation. This in turn shortens the life of the fan motor 1.
The invention provides a magnetic bearing system for rotating machines. The magnetic bearing system gives axial and radial supports for rotating machines such as fan motors, lowers their friction and noise during operation, and thus prolongs the life of rotating machines.